Telephone system



L. POLINKOWSKY.

TELEPHONE SYSTEM.

APPLICATION FILED NOV. 1, 1919.

Patented Nov. 1, 1921.

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TELEPHONE SYSTEM. APPLICATION FILED NOV. 1, 1919.

1,395,595. Patented Nov. 1, 1921.

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TELEPHDNE SYSTEM.

1 APPLICATION FILED NOV-1,1919 1,395,595. Patented Nov. 1, 1921.

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APPLICATION FILED NOV- 1, 1919.

Patented Nov. 1, 1921.

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' contemplated by the present invention will LIPA IE OLINKOW'SKY', O1 ANTWERP, BELGIUM, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK.

YORK, N. Y., A CORPORATION OF NEW TELEPHONE-SYSTEM.

. Application filed November To all whom it may concern:

Be it known that 1,: LIPA PoLiNKowsKr, a citizen of Russia, residing at Antwerp, Belgium, have invented .certain new and useful lmprovements in Telephone Systems, of which the following is a full, concise, and exactdescription. v

This invention relates to telephone exchange systems and more particularly to systems in which machine switching apparz tus is employed for establishing telephone clear,

connections between subscribers lines.

The object of the invention is to provide means for rendering a group of connecting circuits non-selectable when a predetermined number of calls has been extended into such group.

A feature of the invention relates to the provision oi means, in a system wherecalls are extended by automatic switchesinto a group of connecting circuits leading to call. indicator at an operators' position, for rendering the circuits of said group nonselectable to the automatic switches when a given number of calls is awaiting attention at such position.

A further feature or" the invention relates to the provision, in a. system where calls are extended over group of circuits to an open ators position anddisplayed before the op erator by means of an indicator mechanism, of means controlled by said mechanism for rendering non-selectable the circuits of said group. 1' I Such other and further features as are be described more in detail in the following description. r

In the drawings phone exchange system embodying the 1nvention, Figure 1 shows a subscribers line terminating in multiple terminals of finder switches at an automatic exchange. This figure also shows the detailed circuits of a second line finder switch, a group selector and the outgoing end of trunk circuits leading to a distant manual exchange.

Fig. 2 shows the incoming end of the trunk circuit terminating in an operators' cord in the manual exchange, together with a called line in said exchange.

Fig. 3 illustrates a call indicator at the operators position, numerical registers for registering the designation of the called line which illustrate a tele-' Specification of Letters Patent. Patented NOV. 1, 1921.

1, 1919. Serial 'No. 334,921.

preparatory to indicating such designations on the called indicator and a trunk finder for associating said registers with any of the trunks leading to the operators position. Fig. 4 shows the circuits and-apparatus of a register controlling mechanism for controlling the selective operation of the auto matic switches in the first exchange, and also for positioning the registers of the call indicator 'device at the manual operators position. The drawings should be arranged as follows Figs. 1, 2 and 3 taken in order from left to right with Fig. 4 below Fig. 1.

In the system shown a calling subscriber in the automatic exchange may obtain connection either with subscribers lines local to his own exchange or with trunk lines lead ing to operatorspositions in a distant manual exchange. If a call is made'to another subscribers line belonging to the same automatic exchange, the calling subscriber by manipulating his dialsets u the registers of the switch controlling mechanism in Fig. 4 in accordance with the designation of such called line. These registers are thereupon effective to control the operation of the selective switches in the automatic exchange to select and make connection with the desired line. It a call is made to a subscribers line which belongs to a manual exchange the register controlling mechanism is positioned in a similar manner under the control of the calling subscribers sender to register the designation of the called line. In this case, however, only a portion of the registers of the controlling mechanism is effective to control the operation of selective switches in the automatic exchange since a trunk line is nowselected leading to an operators position in the distant manual ofiice. After the calling line has thus been extended over a group selector switch to an operators position in the manual ofiice, a trunk finder switch thereat is automatically operated to find the calling trunk and associate the same with a set of registers. The remaining positioned registers of the switch controlling mechanism in the automatic exchange are then successively restored to their normal positions, and in so doing cause a similar setting of the corresponding registers at the operators position. These latter registers, having been positioned, prepare circuits for the selection of the proper indicating lamps of the call indicator to visually display the digits of the number of the line desired in the manual exchange.

Upon a second call being made in the group of trunks leading to this operators position in the manual exchange a second trunk finder associates the trunk on which said second call appears with another set of registers. As soon as the operator has attended to the first call the second number registered is then displayed upon the call indicator. In accordance with the present invention when two calls are awaiting attention at an operators position, means controlled by the circuits of the trunk finder switches becomes operative to render the remaining trunks of the group non-selectable by the selective switches in the automatic exchange. It is apparent that by slight modifications the circuits may be arranged such that any desired number of calls may be allowed to come in to an operators position before the. remaining trunks are rendered non-selectable.

The first line finder switch shown diagrammatically in Fig. 1, the second line I finder and the group selector shown in detail in Fig. 1 and the register controlling mechanism illustrated inFig. 4 are similar in construction and operation to the apparatus described in detail in an application filed by Polinkowsky and Matthies, June 14, 1919, Serial No. 304,212. .The selective switches employed in this system are of the wellknown power-driven type controlled in accordance with the revertive impulse principle from a set of numerical controlling registers. As is well explained in the above mentioned application, these registers consist of sequence switches each having a series of ten controlling positions. As is also explained in said application the calling subscribers dials are designed to transmit impulses in accordance with the complements of the digits for setting the controlling registers, and further to cause a comparatively long interruption for the last impulse of each series.

It is believed that a more thorough understanding is to be had of this invention from a detailed description of the operation of this system in which it is embodied.

Assume that the subscriber of a line, such as 200 in the automatic exchange, wishes to converse with a subscriber whose line belongs to a distant manual exchange, such as the line 430. The subscriber of the line 200, by removing his receiver from the switchhook, causes in the well-known manner the operation of a first line finder to set its brushes 270, 271 upon the terminals 272 and 273 of the calling line. The starting relay 216 is also energized and a circuit is completed from ground over the armature and contact of said relay, contact 227 (1) of sequence switch 220 of the second line finder switch, through the winding of relay 222 to battery and ground. Relay 222 energizes and closes a circuit from battery, contact 226 (1), through the winding of power magnet 246, back contact and armature of relay 232, front contact and armature of relay 222 to ground at the back contact and armature of relay 231. Power magnet 246 energizes in this circuit and'causes the rotation of the brush carriage of the second line finder. When the brushes 274, 275, 276, 277 make contact with the terminals of the calling circuit a selectable potential is found upon the test terminal 278, relay 212 being ener gized at this time. A circuit is now prepared from battery, contact and armature of relay 212, terminal 278, brush 277 contact 228(1), through the right-hand high resistance winding of relay 234, back contact and right-hand armature of relay 224, contact 210 (1), contact 281 of sequence switch 280, closed in positions 1 to 10, to ground. The test relay 234 energizes and closes a low resistance circuit through its left-hand windcontact and armature of relay 222 to ground 7 at back contact and armature of relay 231. Sequence switch 220 moves from position 1 into position 4.

As sequence switch 220 reaches position 3, and'in the positions thereafter up to position 13, a circuit is closed from ground, contact 213, left-hand armature and back 0011- tact of relay 224, through the windingof relay 235 and thence to battery and ground.

in series with the cut-off relay (not shown) of the calling line. Relay 235 energizes and extends the calling line through to the cord circuit shown in Fig. 1 over sequence switch contacts 221 and 223. Relay 231 is therefore energized in series with the calling line and the retardation coil 237.

In position 4 of sequence switch 220 the selection of an idle register controlling mechanism such as the one shown in Fig. 4 takes place. For this purpose a testing sequence switch 280 is provided to test the idle or busy condition of the register mechanisms, and upon finding an idle one, to associate the same with the circuits of the group selector shown in Fig. 1. The circuit for initiating the testing operation of sequence switch 280 extends from battery, through the winding of said sequence switch, contact 214 1), back contact and armature of relay 232, contact 210 (4), to ground at con tact 281 of sequence switch 280. It will be noted that relays 23 i and 232 are deenergized upon the opening of contact 228 as sequence switch 220 passes out of position 3. The circuits or" the register mechanisms, such as the one shown in Fig. 4, are multi pled to corresponding contacts, as contacts 282, 283, 28 1, of a plurality 01" testing sequence switches 280. The circuits of the register mechanism shown in the drawing are associatedwith the circuits of the group selector when sequence switch 280 is in either position 1 or position 7. It, therefore, the register mechanism shown is idle when sequence switch 280 reaches either position 1 or 7, a circuit is completed from battery through the right-hand winding of relay 323, l, contact 310 (1) of sequence switch 320, conductor 293, contact 282-, contact 2-l3. (4), through the right-hand high resistance winding of relay contact 231 Jun 7 closed in its successive half-positions to ground. The contacts 282 of sequence switch 280 are arranged so that their circuit closing'positions extend over an angular distance sutlicient to insure the closure of the above traced circuit when contact 281 is in one of its half-positions. Relay 23a ener gizes and closes a low resistance circuit through its left-hand winding, contact and armature and through the winding of relay 232 to ground. Relay 232 energizing opens the circuit of sequence switch 280, causing the same to stop, and also closes a circuit from battery through the winding of sequence switch 220, contact 211, front contact and armature of relay 232, contact to ground at contact 281. The sequence switch 220 leaves posit-ion i and moves into position 5. When sequence switch 220 passes out of position a it opens, atcontacts 221 and 223, the bridge across the calling line through relay 231 and retardation coil 237, permitting relay 231 to deenergize. The calling line is nowextended over contacts 221 and 223, closed position 5, to the stepping relay 325 of'the selected register mechanism, ready for the transmission of impulses to register the designation of the called line. The impulse circuit including relay 325 may be traced from battery, through the left-hand winding of said relay, conductor 311, contact 313 of sequence switch 280, contact223 (5), lower armature and contact of relay 235, brushes 275 and 271, terminal 273, over the loop of the calling 7 e, terminal 272, brushes 270 and 27%, front contact and upper armature of relay contact 221 contact 31 1 of sequence switch 280, conductor 312, through the right-hand winding ofrelay 325 to ground.

armature and front contact It may be noted at this point that the register-controlling mechanism shown in Fig. 1 is provided with two sequence switches 320 and 350 for controlling the positioning and the restoration to normal of the register sequence switches. The contacts belonging to the sequence switch 320 are located on the drawing above and to the left of the broken line whereas the contacts controlled by sequence switch 35-9 are located below and to the right or" the broken line. Each of the register sequence switches 100, 110, 120, 130 and .1 10 and the contacts which they control are contained within small rectangles at the bottom of the drawing.

At the time the register mechanism was selected, relay 323 was energized in series with test relay 23 1. A circuit was thereupon closed from ground, over the armature and front contact of relay 323, through the lefthand winding of said relay, contact 335 (1),

through the winding of sequence switch 320 to battery and ground. Sequence switch 320 moves out of position 1. In leaving position 2, sequence switch 320 opens the original energizing circuit of: relay 323 at contact 310, permitting said relay to be deenergized before sequence switch 320 reaches position Sequence switch 320 therefore comes to rest in position 3, and at its contact closes a circuit for the interrupter 316 in series with the primary winding of the dialing tone coil 317. As soon as the stepping relay energizes in series with the calling line and sequence switch 320 reaches position 3 to permit the denergization of relay 323, a circuit is closed from ground, armature and baclr contact of relay of relay 325, through +he left-hand inding of differential relay 329, armature and contact of said relay, contact 330 through the winding of the register 100. to battery and ground. At the same time a. parallel circuit is closed through the right-hand winding of relay 329 to ground at the armature of relay 323. Relay 329 being differential is not encrgized when a circuit is closed for both-of its windingsv The register 100, however, s"arts from position 0. Between positions 0 and 1 oi? register 100, the local contact 103 of saic register closes a short-circuit around th left-hand winding of diilerential relay 329 permitting this relay to energize. The register 100 under the control of its local contact moves into position 1.

calling subscriber on hearing the disdialing tone in his receiver when ce switch 320 moves into position 3, lrnou that he -ay proceed with the operaof his dial. Upon the first interruption I the calling line at the subscribers dial, relay 325 retracts its armature and opens the circuit of the right-hand winding of differential relay 329, which relay thereupon deenergizes. As the line circuit again closes, register 100 is energized once more and moves out of position 1, relay 329 energizes,

the register passes to position 2 and at the next interruption or the line circuit, relay 329 becomes deenergized. This operation continues, the register 100 advancing one position for each interruption of the line until the first series of impulses has been completed. The relay 382 is provided to insure a complete step of register 100 and also of the succeeding registers in case the impulse relay 325 should release its armature quickly due to abnormally short closures of the line circuit. It will be seen that upon the energization of relay 325' a circuit is completed from battery through the winding of relay 382, contact and armature and lefthand winding of relay 329, contact and armature of relay 325 to ground at the back contact and armature of relay 323. Relay 332 therefore ener izes in parallel with the register magnet 100. Belay 382 is quick actin and responds immediately that the armature of relay 325 engages its front contact. On attracting its armature the relay 382 provides ground for the maintenance of the circuit above traced through the windings of relay 329 in substitution of the ground connection that is closed through the armature and front contact of the impulse relay 325. Consequently, once the circuit of register 100 is closed it is maintained closed until the register, which may be comparatively slow in its movement, has had time to start and move to a point where it provides its own independent circuit at the master contact 103. Should the impulse relay 325 deenergize immediately following its energiza ion, the relay 382 insures that the register 190 will take a complete step. The closure of the master contact 103 serves as above described to shunt out the left-hand winding 01 relay 329 so that current now fiows from battery through the winding of the register magnet 100 and also from battery through the winding of relay 382 dircctly to ground at contact 103 without passing through the left-hand winding of relay 329. Therefore, relay 329 energizes in a circuit. through its right-hand winding closed, either to ground over the front contact and armature of relay 325 as above explained, or to ground at the contact and armature of relay 382, provided relay 325 has become deenergized at this time due to an abnormally short impulse. When the relay 329 becomes energized by reason of the circuit. closed at the contact and armature of relay 382, it will be released immediately that the register reaches its position and opens the master contact 103 to cause the deenergization of relay 382. At each retraction 01" the armature of relay 325 a momentary circuit is closed from battery through the winding of relay 334, contact 318 (3), back contact and armature of relay 325, to ground at the back contactand armature of relay 323. Relay 334, however, is made slow to energize and does not attract its armature during brief closures of its circuit. At the last interruption of the line, which due to the construction of the subscribers transmitter is made comparatively long, the circuit of relay 334 is closed for a sufficient interval to permit said relay to energize. A circuit is now completed from battery through the right-hand winding of relay 323 to ground at the armature and contact of relay 334. Relay 323 energizes and closes a circuit through its left-hand winding and contact 335 (3) to drive sequence switch 320 outof position 3. Before sequence switch 320 can reach position 6 the line circuit is again closed and relay 334 deenergizes to in turn cause the deenergization of relay 323. Sequence switch 320, therefore, comes to rest in position 6.

In position 6 of sequence switch 320 a circuit is closed from ground, armature and back contact of relay 323, armature and front contact of stepping relay 325, lefthand winding, armature and-contact of relay 329, contact 330 .(6), through the winding of the register 110 to battery and ground. in parallel to this circuit the right-hand winding of relay 329 is energized over a circuit to ground at armature of relay 323. The register 110 moves out of position 0 and at its local contact 112 short-circuits the left-hand winding of differential relay 329 permitting this relay to energize. The register 119 advances under the control of its local contact into position 1. When the subscribcrs lineis open for'the first time on the transmission of the second series of impulses, relay 325 deenergizes and opens the circuit for the right-hand winding of relay 329. Relay 329 thereupon releases its armature. At the next closure of the line circuit and the resultant energization of the stepping relay 325, the register 110 is again energized and. moves from position 1 into position 2. Thisprocess continues, the register 110 advancing one position for each interruption of the line circuit until the last impulse of the series is transmitted. The relay 382 serves to control relay 329 and register 110 in the manner explained in connection with the setting of the first register 100. The last interruption of the line being relatively long, slow to operate relay 334 attracts its armature as above described and. closes the circuit for the right-hand winding of relay 323. Relay323 completes a circuit for driving sequence switch 320 out of position 6 and into position 8. p

In position 8 of sequence switch 320 a circuit is closed from ground, armature and back contact of relay 323, armature and attracts its armature and causes,

.tion 2.

front contact of relay 325, left-hand winding, armature and contact of relay 329, contact 331 (8) through the winding of register 120 to battery. The register 120 advances from position 9 to position 1 and causes the shortcircuiti-ng of the left-hand winding of relay 329. Relay 329 thereupon attracts its armature. hen the subscriber operates his dial to send the third series of impulses, the first interruption of the line causes the deenergization of relay 325 and the consequent deenergization of relay 329. At the next closure of the line circuit the register 120 is advanced from position 1 into position 2 and relay 329 again operates. This operalion continues until the last impulse of the third series is sent, at which time relay 334 as already explained, the sequence switch 320 to move from position 8 into position 11.

In position 11 of sequence switch 320, the tens register 130 is energized in a circuit from ground, armature and back contact of relay 323, armature and front contactof relay 325, left-hand winding and armature and contact of relay 329, contact 332 (11) through the winding of register 130 to bat tery and ground. Register 130 moves out of position 0 and into position 1 and causes thereby the energization of relay 329. The

calling subscriber on sending the 'fourth series oi impulses causes relay 325 to deenergize in response to each interruption of the line circuit. At the first interruption of the line the circuit for-the right-hand winding of relay 329 is opened at the contact of relay 325 and relay 329 therefor releases its armature. Upon the next closure of the line, the register 120 is again energized and advances from position 1 to posi- This operation continues until the last impulse of the fourth series has been sent, at which time the slow-operating relay 334 attracts its armature and sequence switch 320 is driven from position 11 into position 13.

v In position 13 of sequence switch 320 the units register 140 is energized by means of a circuit from ground, armature and back contact of relay 323, armature and front contact of relay 325, left-hand winding and armature and contact of relay 329, sequence switch contact 332 (13), through the winding of register 140 to battery and ground. In the manner already described the units register 140 is advanced to a position corresuonding to the number of impulses transmitted from the calling subscribers substation. .t the termination of the final series of impulses, relay 334 energizes and closes the circuit for relay 323, which in turn closes a circuit to drive sequence switch 320 out of position 13 and into position 15.

As scenes the first register 100 has been 1 pnsitioned, sequence switch 320advances position 6. A'circuit is then completed for driving sequence switch 350 into position 3. This circuit may be traced from battery through the winding of sequence switch 350, contact 351 (1), contact 353 (6) to ground. In position 3 of sequence switch 350, the fundamental circuit for controlling the brush selection of the group selector shown in Fig. 1 is closed. This circuit may be traced from battery, through the winding of relay 222, contact 242 (5), contact 283, conductor 296 through the winding of stepping relay 355, armature and contact of relay 357 to ground at contact 354 (3). Both relays 222 and 355 are energized. Relay 222 closes a circuit from battery through the winding of sequence switch 220, contact 211 (5), front contact and armatureof relay 222 to ground at the back contact and armature of relay 231. Sequence switch 220 moves out of posi- .tion 5 and into position 6, in which position a circuit is closed for the trip spindle power magnet 248. This circuit may be traced from battery through the winding of magnet 248, contact 215, front contact and armature of relay 222, back contact and armature of relay 231 to ground. The brush-tripping spindle rotates, and for each brushtripping position, the interrupter contacts 250 close a shunt circuit around the stepping relay 355 in the fundamental circuit. At the first deenergization of relay 355, in response to the closure of interrupter contacts 250, a circuit is closed from ground, armature and contact of relay 355, contact 356 (4 to 16), lefthand winding and armature and contact of relay 359, contact 342 (3) of sequence switch 350, contact 102, through the winding of register 100 to battery and ground. A circuit is also closed from battery through the right hand winding of relay 359 to ground at the armature of relay 355. The relay 359 being differential, does not attract its armature when both windings are energized. The register 100, however, energizes and moves out of the position to which it was set from the calling substation. In passing from one position to the next, the register 100 at its local contact 103 short-circuits the left-hand winding of differential re ay 359 permitting this relay to attract its armature. )Vhen the short-circuit at interrupter contact 250 is removed from the fundamental circuit and the stepping relay 355 again energized, the righthand winding of relay 359 is opened and this relay releases its armature. This operation continues, the brush tripping spindle rotating from one position to the next until the register 100 is restored to its zero position. The relay 383 has a function similar to relay 382. This relay likewise operates in parallel to the successive registers in-a circuitclosed through the left-hand winding of the dif ferential relay 359to ground at the armature at the st p ng el y +W neeersi relay 383 locks up at its contact and armature and provides a substitute'circuit for the registers to insure their complete operation from one position to the next in the event that the stepping relay 355 again becomes energized before the register has had time to start. In the case assumed, where a call is being extended to a manual exchange, the register 100 has been advanced to such a position as to control the-brush tripping spindle to select a set of brushes having access to a level of trunks leading to the desired manual exchange. Upon the next deenergizationof relay 355, after register 100 has reached'position 0, a circuit is closed to drive the sequence switch350 out of position 3 and into position 4. This circuit leads from battery, through the winding of sequence switch 350, contact 341 (3), contact 102 (0), contact 342 (3), contact'and armature and lefthand winding of relay 359, contact 356 to ground at the back contact and armature of relay 355. In a circuit parallel to the circuit just traced, relay 357 is energized and at its armature maintains the fundamental circuit open, while sequence switch 350 is passing into position 4. Relay 222'deenergizes as soon as the interrupter contacts 250- have been'opened after the fundamental circuit is interrupted at the sequence switch contact 354. Relay 222 closes acircuit from battery through the winding of sequence switch 220, contact 225 (6), back contact and armature of relay 222 to ground at the back contact and'armature of relay 231. Sequence switch220 moves into position 7 In position 7, relay222 is again energized in a circuit from battery-through the winding of said relay, contact 243 (7) contact 282, conductor 293, contact 329 (4) to ground at back contact and armature of relay 37 5.

In position 7 of sequence switch 220, the brush-carriage power magnet 241 of the group selector is energized in the following circuit: battery, through the winding of said magnet, contact 244 (7), back contact and armature of relay 232, front contact and armature of relay 222, back contact and armature of relay 231 to ground. The brush carriage is rotated to advance its brushes 251,

252 and 253 over the terminals'of trunks such as terminals 256, 257 and 258 of the selected level of trunks. An idle trunk is one which is identified by means of a se lectable potential on the test terminal 253. Then the rotating brushes reach the terminals of an idle trunk leading to the operators position shown in Fig. 2, a circuit is closed from battery, resistance 402, armature and back contact of relay 404, contact 401, of sequence switch400, closed in either position 1, 7 or 13, through the winding of relay 403, testterminal 258, test brush 253, term1nal 223 (7), through the right-hand hlgh resistance winding of test relay 234,

path shunts out the righthand high resistance winding of relay 234 and thereby reduces the potential on multiples of terminal 258 to'render the selected trunk circuit busy to other group selector switches. The relay 7 232 energizes and opens at its back contact, the power circuit for themagnet 241 thereby causing the brush carriage to cease its rotation. Relay 232 also closes a circuit as follows to drive sequence switch 220 over position 8 and into position 9: battery, through the winding of sequence switch 220, contact 7 211 (7 to 8), front contact and armature of relay 232', front contact and armature of relay 222 to ground at the back contact and armature of relay 231. 1

The relay 403 in the test circuit of the outgoing end of the trunk is energized in series with relays 234 and 232. Relay 403 by attracting its left-hand armature closes a substitute circuit for itself independent of sequence switch'contact 401. At its righthand armature relay 403 closes a circuit from battery through the right-hand winding of relay 404, right-hand armature and contact of relay 403, test conductor 411 through the right-hand low resistance winding ofrelay 414 in the manual exchange, through the left-hand high resistance winch ing of relay 414 to ground at the armature of relay 415. Relay 404 being marginal does not operate in series with the left-hand winding of relay 414. Relay 414 energizes and closes a circuit from battery over'its front contact and armature, through the windings of relays 416 and-415 to ground. Relay 416-by attracting its armature connects the right-hand low resistance winding of relay 414 directly to ground in shunt of the left-hand winding of relay 414. Since the resistance in series with the relay 404 is now reduced, this relay operates and closes a circuit to conductor 411 for its left-hand high resistance winding in parallel with its right-hand winding. In parallel with the circuit for relay 416, acircuit is closed from battery, front contact and armature of relay 414, armature and back contact of relay 420, lamp 417, right-hand armature and back contact of relay 421 through the windings to automatically select the trunk upon which i the call exists to associate the same with an idle set of registers 510, 520, 530 and 540. A circuit for initiating the operation of the trunk finder may be traced from ground, right-hand armature and contact of relay 418, conductor 474, armature and back contact of relay 462, through the winding of the brush carriage power magnet 461 of the trunk finder, contact 475 of sequence switch 450 to battery. The brushes 431, 432, 433 and 434 are rotated over the terminals of circuits individual to the different trunks incoming to the operators position to search for the particular trunk over which the call has been extended. When the test brush 434 engages test terminal 460 of the proper trunk, a circuit is closed from battery, front contact and armature of relay 414, armature and back contact of relay 420, left-hand armature and front contact of relay 418, terminal 460, brush 434, contact 455 (1), through the right-hand high resistance winding of test relay 464, back contact and right-hand armature of relay 457, contact 453 (1) to ground. Relay 464 energizes and closes a low resistance path through its lefthand winding and the Winding of relay 462. This low resistance circuit decreases the potential on multiples of terminal 460 so as to render the same non-selectable to other trunk finders. Relay 462 energizing, opens the circuit of magnet 461 and also closes a circuit from battery through the winding of sequence switch 450, contact 456 (1), front contact and armature of relay 462, conductor 474 to ground at the right-hand armature of relay 418. Sequence switch 450 advances into position 4.

lVhen sequence switch 450 leaves position 2, the circuit for relays 464 and 462 is open at contact 455, but the terminal 460 is maintained busy in position 3 by means of a direct connection to ground over contact 466 (3) and the back contact and armature of relay 452. As soon as sequence switch 450 reaches position 3, a circuit is closed from ground, contact 453, right-hand armature and. back contact of relay 457, through the right-hand high resistance winding of relay 464, contact 455, brush 432, terminal 479, through the windings of relays 426 and 427, back contact and armature of relay 420, armature and front contact of relay 414 to battery and ground. Relays 426 and 427 do not energize in series with the high resistance winding of relay 464. However, as soon as relay 464 attracts its armature, it closes a low resistance circuit through its left-hand winding and the winding of relay 462 to ground in parallel to the right-hand winding of relay 464. Relays 426 and 427 now become energized. When relay 426 attracts its armature a circuit is closed from battery, front contact and armature of relay 414, armature and back contact of relay 420, left-hand armature and contact of relay 426 through the left-ha-nd high resistance winding of relay 421, to ground "through the winding of relay 419. Relay 421 energizes and opens the circuit of relay 418.

Since the sequence switch 220 of the group selector in the automatic exchange has already reached position 9, the operation of relay 427 completes the fundamental circuit. from the controlling registers in the automatic exchange through to the stepping relay 452 at the call-indicator mechanism. This fundamental circuit may be traced from battery, contact 459 (4), through the winding of stepping relay 452, left-hand armature and back contact of relay 457, brush 431, conductor 423, front contact and lower armature of relay 427, conductor 413,. terminal 257, brush 252, contact- 242 (9), contact 283, conductor 296, relay 355, armature and contact of relay 357, contact 358 (6), left-hand armature and back cont-act of relay 378, conductor 297, contact 284, contact 255 (9), brush 251, terminal 256, conductor 41, upper armature and front contact of relay 427, to ground. It will be observed that the sequence switch 350 was advanced into position 6 by means of a circuit includ ing contact 351 (4) and contact 353 (7 to 13), as soon as the sequence switch 320 leaves position 6. Both relays 355 and 452 energize in the above traced fundamental circuit. Relay 452 closes a circuit to drive sequence switch 450 into position 5. This circuit may be traced from battery through the winding of sequence switch 450, contact 467 (4) to ground. at the front contact and armature of relay 452. In position 5 of sequence switch 450 the register 510 which determines the selection of the thousands indicator lamps is placed under the control of the thousands register 110 in the automatic ex change. The register 110 is now ready to be restored to its normal position and control the advance of the register 510 in order to select the proper digital indicator lamp in the thousands row.

Relay 452 closes a circuit from battery through the winding cf register 510. Con act 521 of the suaccedingregister 520. contact of sequence switch 459 tn ground at the front contact and armature of relay 452. The reg ster 519 starts out from position 1 and moves through its successive positions. In passing through ts half po sitions. the register :19 closes Contact At each closure the contact the fol lowing alternate circuit is closed for relay 452: battery, center 9, through the winding of relay to round at contact 513.

This substitute circuit maintains the ener gization of relay 452, but shunts cut the stepping relay in the fundamental circuit. Upon the first deenergization of the stepping relay 355 in response to the closure of contact 513, a circuit is established from ground, armature and contact of relay 355, contact 356 (6), 1eft-band winding and 'mature and contact of relay 359, contactthe position to which it was adjusted by the calling subscribers dial. In moving through each succeeding position, the local contact 112 short-circuits the left-hand winding of differential relay 359 permitting this relay to attract its armature. The register 110 advances under the control of this local contact intoits next position. As soon as contact 513 of register 510 is again opened, the relay 355 energizes and opens the circuit for the right-hand winding of relay 359. Relay 359 releases its armature. At the next closing position of contact 513 relay 355 is Sher"- circuited and releases its armature closing the above-traced circuit for register 110. Register 110 thereupon advances into its next position. This operation obtains until register 110 reaches position zero at which time the following circuit is closed: battery, through the winding of sequence switch 350, contact 341 (6), contact 102 (0), contact 342 (6), contact 111 (0), contact 343 (6), contact and armature and left-hand winding of relay 359, contact 356, to ground at the contact and armature of relay 355. The relay 357 is also energized in the circuit parallel to the one just traced. Relay 357. opens the fundamental circuit while the sequence switch 350 energizes and moves from position 6 into position 7 )Nhen the contact 5130f register 510 is opened following the opening of the fundamental circuit at 'the automatic exchange, relay 452 deiinergizes and closes the following circuit: ground, armature and back contact of relay 452, contact 466 (5), through the winding of sequence switch 450 to battery. Sequence switch 450 moves into position 6. )Vhen sequence switch 450 leaves position 5, it opens the driving circuit of the register 510 sothat this register comes to rest in a position determinedv by the setting of the register 110 in the auto,- matic exchange.

hen the calling subscriber completes the sending of the third series of impulses and sequence switch 320 moves into position 11,

sequence switch 350 is advanced into posi tion 9 by means of a circuit from battery through the winding of sequence switch 350,

contact 347 (7), contact 348 of sequence switch 320 to ground. In position 9 of sequenee switch 350, the fundamental circuit .is again established and relays 355 and 452 become energized. Relay 452 closes a circuit from ground over its armature and front contact, contact of sequence switch 450 to battery and 467 (6) through the winding sive positions under the control of the register 120. A circuit for operating register 520 may be traced from battery through the winding of said register, contact 532 (1) of register 530, contact 468 (7), front contact and armature of relay 452 to ground. In a manner similar to that described, the register 520 short-circuits stepping relay 355 by means of its contact 523. At each retraction of the armature of relay'355, a circuit is closed from ground over the armature and contact of said relay, contact 356, left-hand winding and armature and contact of relay 359, contact 345 (9), contact 121 of the register 120 through the winding of said register to battery and ground. Y hen register 120 reaches position zero under the control of. this circuit, sequence switch 350 is driven into position 10 by means of the following circuit: battery, through the winding of sequence switch 350, contact 341 (9), contact 102 (0), contact 342 (9), contact 111 (0), contact 343(9), contact 121 (O),contact 345 (9), contact and armature and left-hand winding of relay 359, contac 356 to ground at th contact and armature of relay 355. Relay 357 is also energized inaparallel circuit. When and closes a circuit from ground over its armature and back contact, sequence switch contact 466 (7) through thewinding of sequence switch 450, to battery. Sequence switch 450 moves out ofposition 'i and into position 8. As soon as the subscriber has completed the-sending of the fourth series of impulses and sequence switch 320 moves into position 13, a circuit is closed from battery through the winding of sequence switch 350, contact 351 (10), contact 353 of se quence switch 320 to ground. Sequence switch 350 moves fromposition 10 into position 11.

The fundamental circuit is nowclosed at contact 358 and relays 355 and 452, energize once more. Upon the energization of'relay 452, sequence switch 450 is driven into position 9 by means of a circuit including contact 467 (8) and the contact and armature of relay 452. A cir-' tion of relay 355, the following circuit is closed: ground, armature and contact of relay 355, contact 356, left-hand winding and armature and contact of relay 359, contact 346 (11), contact 131 through the winding of register 130 to battery and ground. The register 130 advances through its successive positions and on reaching position 0 closes a circuit to drive sequence switch 350 out of position 11 and into position 12. This circuit may be traced from battery through the winding of said sequence switch, contact 347 (11), contact 131 (0), contact 346 (11), contact and armature and left-hand winding of relay 359, contact 356 to ground at contact and armature of relay 355. On the first opening of the contact 533 following the in terruption of the fundamental circuit at the automatic exchange, relay 452 releases its armature and closes a circuit including contact 466 to drive sequence switch 450 into position 10.

When the calling subscriber has transmitted the last series of'impulses and sequence switch 320 moves into position 15, the following circuit is closed to drive sequence switch 350 out of position 12 and into position 14: battery, through the winding of sequence. switch 350, contact 341 (12) to ground at contact 333 (15'). With sequence switch 350 in position 14, the fundamental.

circuit is again closed at contact 358 and relays 355 and 452 become energized. Relay 452 closes a circuit including its front contact and contact 467 (10) for driving sequence switch 450 into position 11. The final register 140 in the automatic exchange is now restored to its normal position to control the setting of the register 540 of the call-indicator mechanism. The register 540 is energized in a circuit from battery through its winding, contact 532, of register 530, contact 468 (11) to ground at the front contact and armature of relay 452. At each closure of the contact 543 of register 540, the stepping relay 355 in the fundamental circuit is denergized. For each de'elnergization of relay 355, a circuit is closed from ground, armature and back contact of such relay, contact 356, left-hand winding and armature and contact of relay 359, contact 346 (14), contact 141, through the winding of register 140 to battery and ground. As soon as relay 355 deenergizes after register 140 has finally reached its normal position 0, a circuit is closed from battery through the winding of sequence switch 350, contact 347 (14), contact 144 (0) of register 140, back contact and armature of relay 374, contact 141, contact 346 (14), contact and armature and left-hand winding of relay 359, contact 356, to ground at the contact and armature of relay 355. Sequence switch 350 advances from position 14 into position 16 and relay 357 opens the fundamental circuit in the manner above described. When contact 543 opens after the interruption of the fundamental circuit, relay 452 deenergizes and closes a circuit including contact 466 to drive sequence switch 450 out of position 11 and into position 14.

The numerical designation of the called line in the manual exchange has thus been registered on the registers 510, 520, 530 and 540 ready to select the proper number lamps from the thousands, hundreds, tens and units rows to display the called number before the operator. At the operators position, there is provided a set of re isters diagrammatically shown at 510, 520 530 and 540 upon which the designation of a second call in coming to this operators position may be registered. There is also provided a second trunk finder switch shown at 531 for associating a callin' trunk with the register 510', 520', etc. The sequence switch 490 corresponding to sequence switch 450 is arranged to control the circuits of the second trunk finder switch 531.

Assuming the number indicator lamps are idle at the time sequence switch 450 reaches position 14, a circuit will be closed from battery through the winding of sequence switch 450, contact 456 (14) to ground at contact 493 of sequence switch 490. Sequence switch 450 thereupon advances into position 16 which is the position for displaying the called number upon the indicator lamps. Assume, for example, the call is represented by lamp 550 in the thousands row, lamp 551 in the hundreds row, lamp 552 in the tens row and lamp 553 in the units row. The circuit for lamp 550 is closed from battery, contact 475 (16), contact 524 closed in an even position, lamp 550, contact 554 to ground at contact 451 16). The circuit for lamp 551 is closed from battery, through the winding of magnet 560, contact 458 (16), left-hand armature and back contact of relay 561, lamp 551, contact 555, to ground at contact451 (16). The circuit for lamp 552 isclosed from battery, contact 459 (16), lamp 552, contact 556, contact 454 (16) to ground. The circuit for lamp 553 is closed from battery, contact 459 (16), lamp 553, contact 557 to ground at contact 454 (16). It will be observed that the registers 510, 520, 530 and 540 of the indicating mechanism are set up to positions equal to the number of positions through which the registers 110, 120, 130 and 140 are driven in order to reach their zero positions after having been set under the control of the calling subscribers line. Therefore the registers 510, 520, etc., are adjusted to positions which correspond to the complements of the positions to which registers 110, 120, etc, are set from the calling subscribers station. In order that the lamps of the call indicator may display the actual digits of the called number rather than the complements of such digits, it is only necessary that they be numbered in such a manner that the registers 510, 520, etc, in being set upto a given position will select a lamp in its corresponding row whose number is the complement of the number corresponding to the position to which such register is adjusted.

W'hen sequence switch 450 leaves position 14 and moves into position 15 at the time the called number is displayed on the indicator. lamps, the holding circuit of relays 464 and 462 is opened at contact 455. Relays 426 and 427 which are included in this circuit are deenergized, but relays 464 and 462 are maintained energized by means of a substitute circuit from battery, contact and armature of relay 414, armature and contact of relay 420, left-hand armature and back contact of relay 418, brush 433, contact 469 (15-1-16) through the left-hand winding, contact and armature of relay 464 to ground through the winding of relay 462. When relay 426 deenergizes, it opens the circuit of the left-hand high resistance winding of relay 421, but this relay is now maintained energized over its low resistance winding. With relay 421 energized and relay 426 denergized, a circuit is completed from battery, front contact and armature of relay 414, armature and back contact of relay 420, right-hand armature and contact of relay 426, calling lamp 442, left-hand armature and contact of relay 421 through the winding of relay 419 to ground.

At the time the sequence switch 350 in the automatic exchange leaves position 14 and moves into position 16 after the last reg: .ister 540 at the indicator mechanism has been positioned, the register controlling mechanism is released from the connecting circuit of the group selector. The release of this mechanism is brought about by the deenergization of relay 222, the circuit of which is opened by relay 375. When sequence switch 350 passes through position 15 it closes a circuit as follows for relay 375: battery, through the left-hand winding of said relay, contact 376 (5+15),lower contact 366 (15) to ground at the left-hand contact 354 (4+18). Relay 375 at its armature and back contact opens the circuit hereinbefore traced which up to the present time has been holding the relay 222 energized: Relay 222, by releasing its armature closes a circuit from battery through the winding of sequence switch 220, contact 225 (9), back contact and armature of relay 222, back contact and armature of relay 231 to ground. The sequence switch 220 moves from position 9 into position 10. At contacts 221 and 223, the calling subscribers line is disconnected from the stepping relay 325 and connected through to relay 231 and retardation coil 237. At contacts 255 and 242, the fundamental circuit leading from the register controlling mechanism is disconnected from the trunk 412, 413 and said trunk is connected over contacts 255 and 247 through to the cord circuit of the group selector switch. hen sequence switch 220 of the group selector cord circuit moves into position 10, a circuit is closed from battery through the winding of said sequence switch, contact 217 (10), back contact and armature of relay 262 to ground. Sequence switch 220 is driven into position 11.

When the stepping relay 325 at the register controlling mechanism releases its armature as sequence switch 220 moves out of position 9, a circuit is closed from ground,

armature and back contact of relay 323, armature and back contact of relay 325, contact 318 (15) through the winding of sequence switch 320 to battery. Sequence switch 320 moves into position 16. In position 16, of sequence switch 320,a circuit is closed from battery through the winding of sequence switch 350, contact 341 (16), contact 102 (0), contact 342 (16), contact 111 (0), contact 343 (16), contact 121 (0), contact 345 (16), contact 329 (16), to ground at the back contact and armature of relay 375. Sequence switch 350 advances into position 17. A circuit is then closed from battery through the winding of sequence switch 350, contact 347, contact 131 (0), contact 346 (17), contact 329 (16) to ground at the back contact and armature of relay 320. Sequence switch 350 moves into position 18 where a circuit is completed to drive it into its normal position 1. This circuit may be traced from battery, through the winding of sequence switch 350, contact 347 (18), cont-act 144 (0), back contact and armature of relay 374, contact 141 (0), contact 346 (18), contact 329 (16) to ground at the back contact and armature of relay 320. In position 1 of sequence switch 350, sequence switch 320 is driven from position 16 into position 18 by means of a circuit as follows: battery through the winding of sequence switch 320, contact 335 (16) to ground at contact 349 (1) of sequence switch 350. In position 18 of sequence switch 320, a circuit is closed from battery through the winding of said sequence switch, contact 318, (18), back contacts and armatures of relays 325 and 323 to ground. Sequence switch 320 moves into position 1. The register controlling mechanism is now completely restored to its normal position.

When the operators attention is attracted by the lighting of the calling lamp 442, she observes the number which is displayed upon the call indicator and seizing a plug 443 of the trunk on which the call appears, inserts it into jack 444 of the called line 430. Relays 428 and 420 are now energized in parallel circuits over the sleeve of plug 443 and sleeve of the jack 444 to ground through the left-hand winding of relay 445. The relay 428, by attracting its armature places an impedance 446 in bridge of the trunk 412, 413. Relay 262 in the automatic exchange is now energized in series with the impedance 446 and attracts its armature to close the following circuit: battery through the winding of sequence switch 220, contact 211 (11) front contact and armature of relay 262 to ground. Sequence switch 220 thereupon advances into position 12 which is the talking position. The relay 420, by attracting its armature, opens the circuit of relay 421. iielay 421 deenergizes and opens the circuit of the calling lamp 442.

Relay 420 also opens the circuit which, up to this time has been maintaining the energization of relays 462 and 464. Relay 464 releases its armature to establish a circuit from battery through the left-hand winding of relay 457, contact 478, (16), back contact and armature of relay 464 through the winding of relay 462 to ground. Relay 457 energizes and closes a circuit from battery through the winding of sequence switch 450, 'ight-hand winding, contact and armature of relay 457, contact 453 to ground. Se quence switch 450 advances under the control of this circuit from position 16 to position 17. In position 17 of sequence switch 450, registers 510, 520, 530 and 540 are returned to their normal positions. The circuits for the return of these registers include their respective contacts 515, 522, 535 and 545 and the contacts 473 and 438 of sequence switch 450. lVhen the last register has reached its normal position, a circuit is completed from battery through the winding of sequence switch 450, contact 467 (17), contact 516, contact 526, contact 536 and contact 546 to ground. Sequence switch 450 thereupon advances from position 17 to position 1 ready to control the operation of the trunk finder on the incoming or" another call. I

The operator, by depressing ringing key 435, applies ringing current to the line of the called subscriber. At the termination of the conversation, the calling subscriber restores his receiver to the switchhook and relay 231 releases its armature. Relay 231 opens the circuit of relay 262'which, by deenergizing, closes a circuit to drive sequence switch 220 into position 13. The circuit of sequence switch 220 is traceable from battery through the winding of said sequence switch, contact 217 (12), back contact and armature of relay 262 to ground. In position 13, a circuit is closed from bat tery through the winding of sequence switch 220, contact 225 (13), contacts and armatures of relays 222 and 231 to ground. Sequence switch 220 moves into position 17. The brush carriage is now restored to its normal position by the power magnet 241 which energized in a circuit from battery through the winding of said magnet, contact 244 (17), back contact and armature of relay 232, contact 210 (17) to ground at contact 281. When the brush carriage reaches its home position, relay 232 operates in a circuit including contact 226 and brush 254. Relay 232, by energizing, closes a circuit from battery through the winding of sequence switch 220, contact 211, front c011- tact and armature of relay 232, contact 210 (17) to ground at contact 281. Sequence switch 220 moves out of position 17. When the called subscriber restores his receiver to the switchhook, relay 447, which is energized in series with the called line, releases its armature and extinguishes the called line supervisory lamp 448. The operator thereupon removes the plug 443 from jack 444 of the called line.

In order that only a predetermined number of unanswered calls may be extended to a given operators position, an arrangement is provided in the system shown for rendering the trunks leading to the operators position non-selectable to the group electors in the automatic exchange. There is provided individual to the group of trunks leading to an operators position in the manual exchange, a circuit 441 which extends from a relay 406 in the automatic exchange to the contact 449 of the manual switch associated with the operators position. ii hen two calls have been registered on the registers such as 510, 520, 530, 540 of the indicating mechanism and are awaiting the attention of the operator, the circuit 441 is so affected as to automatically render non-selectable the remaining trunks 412, 413 of the group leading to the operators position. Consider, for example, that a call has been registered on the registers 510, 520, 530 and 540 by means of the trunk finder switch shown in detail and sequence switch 450 is standing in position 4. 11"- now, a second call is extended to the perators position and the designation of the called line registered upon a second set of registers 510, 520, 530, 540 by means of a second trunk finder switch 5-31, the sequence switch 490 01 such second finder switch will be standing in some position between 1 and 16. Therefore, both contact 486 of sequence switch 450 and contact 496 of sequence switch 490 will be open to sever the following circuit which normally maintains relay 406 energized: battery,

conductor 468, either contact 486 or contact 496, conductor 470, contact 449, conductor 441 through the winding of relay 406 to ground. The switch 449 is maintained closed by a plug or any other suitable means during the time the operator is at her position. l/Vhen relay 406 releases its armature, a circuit is closed from battery through the winding of sequence switch 400, contact 405, closed in either position 1, 7 or 13, back contact and armature of relay 406 to ground. Sequence switch 400 advances from the position in which it happens to be standing to the next succeeding position, which will be either position 4, 10 or 16. lVhen sequence switch 400 moves either into position 4, 10 or 16, it closes at its contact 407, a circuit including contact 408 of sequence switch 410 for driving sequence switch 410 either into position 4, 10 or 16. At contacts such as 401 of sequence switch 400 and contact 424 of sequence switch 410, one of which contacts is provided for each trunk 412, 413, the test conductors 411 of all the remaining trunks of the group are opened to render said trunks non-selectable to the group selectors. If a group selector advances its test brush 253 on to test terminal 258 of any one of these trunks during the time contacts 401 and 424 are in positions 4, 10 and 16, no selectable potential will be found on the terminal 258 and consequently the corresponding trunk circuit will not be taken for use.

As soon as sequence switch 450 associated with the set of registers 510, 520 and 530 advances in position 16, to display the number of the wanted line on the call-indicator lamps, contact 486 is again closed and relay 406 becomes energized in a circuit above traced. Relay 406 now establishes acircuit from battery through the winding of sequence switch 400, contact 405 closed in either position 4, 10 or 16 to ground at the front contact and armature of relay 406. Sequence switch 400 therefore moves either in position 1, 7 or 13 and sequence switch 410 advances into a similar position by means of a circuit closed over contact 407 of sequence switch 400. Test conductors 411 of the trunks are now closed so that other calls may be extended to the operators position. It is apparent that by a suitable modification of the arrangement disclosed other register sets and trunk finders may be provided at the operators position together with means whereby any desired number of calls may be stored up at the operators position before the remaining trunks of the group are rendered non-selectable.

It will be noted that the indicator lamps display the figures of called numbers in accordance with the decimal system, whereas the registers in the automatic exchange are adapted to translate the figures of the decimal system into a system suitable for controlling the operation of the selective switches. There I is, therefore, provided means whereby the registers at the call indicator mechanism are capable of re-translating the figures received from the registers at the automatic exchange into the decimal system. If the hundreds register 120 is adjusted to an odd position, relays 373 and 374 are energized in a manner similar to that described in the above entitled application, Serial No. 304,212, filed June 14, 1919. The units register 140, therefore, makes an additional rotation and consequently register 540 passes also through an additional cycle. Register 540 on passing through position 11% closes a circuit for relay 561 at contact 544. Relay 561 energizes and locks up over a circuit including contact 471. The relay 561 having its left-hand armature attracted, a circuit is now closed over contact 555 for the odd lamp 559.

It the thousands register 110 in the automatic exchange is advanced to an odd position, a circuit is closed for relay 360 when sequence switch 320 passes through position 5. Relay 360 being energized, the register 110 is first restored to position 9 and then later after register 120 has been restored register 110 is returned to zero causing the register 520 to advance an additional step. This causes the closure of contact 524 in one of its odd positions, 3, 5, 7, 9, 11. Contact 524 being closed in its odd position the odd thousands lamp 562 is lighted in a circuit including contact 5540 v What is claimed is:

1. In a telephone exchange system, telephone lines, an operators position, an indicating mechanism at said position, a group of trunks leading to said position, said indicating mechanism being common to the trunks of said group, means for extending said lines over said trunks to the operators position, and means controlled by said indicating mechanism for rendering said trunks non-selectable when a predetermined number of lines have been extended to the operators position.

2. In a telephone exchange system, telephone lines, an operators position, an indicating mechanism at said position for visually indicating the numerical designations of called lines, a group of trunks leading to said position, means for extending said lines over said trunks to the operators position, and means controlled by said indicating mechanism for rendering said trunks non-selectable when a predetermined number of lines have been extended to the operators position.

3. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an indicating mechanism at said position, an automatic switching device for associating said trunks with said indicating mechanism, means for extending said lines to the operators position over said trunks, and means controlled by'said switching device torrendermg said trunks non-selectable when a predetermined number of lines have been ex tended to the operators position.

4. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an indicating mechanism at said position, a plurality of trunk finders for associating said trunks with said indicating 'mechanism, means for extending said lines to the operators position over said trunks, and means controlled by said trunk finders for rendering said trunks non-selectable when a predetermined number of lines have been extend ed to the operators position.

5. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an indicating mechanism at said position, a plurality of trunk finders for associating said trunks with said indicating mechanism, means for extending said lines to the opera tors position over said trunks, and means controlled jointly by said trunk finders for rendering said trunks non-selectable when a predetermined number of lines have been extended to the said position.

6. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an indicating device at said position, a set of registers for operating said indicating device, a switch for associating said set of registers with said trunks, means for extending said lines to the operators position over said trunks, and means controlled by said switch for rendering said trunks non-selectable when a given number of lines have been extended to the operators position.

7. Ina telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an inclicating device at said position, a set of registers for operating said indicating device, a trunk finder for associating said set of registers with said trunks, means for extending said lines over said trunks to the operators position, means operated over said trunks for registering the designation of a called line on said register set, and means controlled by said tfunk finder for rendering said trunks non-selectable when a given number of lines have been extended to the operators position.

8. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an indicating device at said position, a plurality of sets of registers for operating said indicating device, a plurality of automatic switches for associating said register sets: with said trunks, means for extending said lines over said trunks to the operators position, and means controlled by said automatic switches for rendering said trunks nonselectable when a given number of lines have been extended to said position.

9. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position, an indicating device at said position, a plurality of sets of registers for operating said indicating device, a plurality of automatic switches for associating said register sets with said trunks, means for extending said lines over said trunks to the operators position, and means controlled jointly by said automatic switches for rendering said trunks non selectable when av given number of lines have been extended to said position.

10. In a telephone exchange system, telephone lines, an operators position, a group of trunks leading to said position. an indicating device at said position, a plurality of sets of registers, a plurality of trunk finders for associating said sets of registers with said trunks, means for extending said lines over said trunks to the operators position, means operated over said trunks for registering the designations of called lines on said sets of registers, means controlled by said register sets for operating .said in dicating device in accordance with the designations registered, and means for rendering said trunks non-selectable when a given number of designations have been registered on said register sets.

11. In a telephone exchange system, tele phone lines, an operators position, a group of trunks leading to said position, an indicating mechanism at said position common to the trunks of said group, means for extending said lines over said trunks to the operators position, and means controlled by said indicating mechanism for opening one of the conductors of each of said trunks to render the same non-selectable when a given number of lines have been extended to said position.

12. In a telephone exchange system, tele phone lines, an operators position, a group of trunks leading to said position, each trunk comprising two talking conductors and a test conductor, an indicating mechanism at said position common to the trunks of said group, means for extending said lines over said trunks to the operators position, and means controlled by said indicating mechanism for opening the test conductors of each of said trunks to render the same non-selectable when a given number of lines have been extended to the operators position.

13. In a telephone exchange system, tele phone lines, an operators position, an indicating mechanism at said position, a group of trunks leading to said position, said mechanism being common to said group of trunks, selective switches for extending said lines over the trunks of said group to the operators position, and means controlled by said indicating mechanism for rendering said trunks non-selectable to said selective switches when a given number of lines have 7 been extended to said position.

14-. In a telephone exchange system, telephone lines, an operators position, a number indicating device at said position, a group of trunks leading to said position, selective switches, a register sender, means for registering the designations of called lines on said sender, means operated by said sender for controlling the operation of said switches to extend said lines over said trunks to the operators position, means controlled by said sender for indicating the designations of called lines on said indicating device, and means controlled by said device for rendering said group of trunks nonselectable to the selective switches 'when'a given number of lines have been extended to the operators position.

15. In a telephone exchange system, an exchange, lines terminating in said exchange, a second exchange, an operators position in the second exchange, a number indicator mechanism at said position, trunks leading from tie first exchange to the operators position in'said second exchange, selective switches for extending said lines over said trunks to the operators position,

and means controlled by said indicator mechanism for renderingsaid trunks. nonselectable to said switches when a g'ven number of lineshave been extended to the operators position.

In witness whereof, I hereunto subscribe my name this 11th day of October A. D., 1919.

LIPA POLINKOWSKY. 

